Quantitative assessment of gene methylation in neoplastic and non-neoplastic gastric epithelia using methylation-specific DNA microarray.

A fiber-type DNA microarray was used to calculate methylation rates (MR) of four tumor suppressor genes, lysyl oxidase (LOX), p16, RUNX3, and tazarotene-induced gene 1 (TIG1). MR were calculated in 26 primary gastric cancers and corresponding non-neoplastic gastric epithelia, and the results were compared to those of conventional methylation-specific polymerase chain reaction (MSP). MR ranged from 0.1% to 69.1% (mean, 18.3%) for LOX, 0.5-74.1% (mean, 15.7%) for p16, 0.2-76.5% (mean, 22.7%) for RUNX3, and 0.6-41.2% (mean, 5.8%) for TIG1 in primary gastric cancers, and from 0.1% to 25.8% (mean, 8.7%) for LOX, 1.0- 23.2% (mean, 10.3%) for p16, 0.7-25.1% (mean, 5.5%) for RUNX3, and 1.8-27.6% (mean, 11.4%) for TIG1 in corresponding non-neoplastic gastric epithelia. Although MR varied significantly across different samples for both neoplastic and non-neoplastic gastric epithelia, high-level methylation (MR >40%) was cancer specific and was observed in 19.2%, 19.2%, 30.8%, and 3.8% of primary gastric cancers for LOX, p16, RUNX3, and TIG1, respectively. All samples with high-level methylation, as well as some samples with low MR (particularly <10%) were judged to be methylation positive on conventional MSP. Quantitative analysis of gene methylation using methylation-specific DNA microarray is a promising method for cancer diagnosis.

[An autopsy case of periampullary carcinoid with amyloid stroma and type 1 neurofibromatosis].

A 67-year-old woman presented with a chief complaint of malaise. CT showed a pancreatic head tumor 5 cm in diameter with calcification. It also showed multiple liver metastases and bile duct dilatation. Esophagogastroduodenoscopy showed deformation and stenosis on the superior and inferior side of the duodenal angle due to a papillary tumor. Thus, retrograde insertion of an endoscope was difficult, and a diagnosis of a carcinoid tumor was obtained by biopsy. After disclosing the diagnosis to the patient, we explained the necessity of treatment. However, the patient refused all proposed treatments, and therefore, we merely provided treatment of her symptom. The patient died of liver failure approximately 3 months later. At autopsy, multiple neurofibromas and café-au-lait spots were observed on the body surface. The tumor was a carcinoid tumor with distant metastases which originated from the duodenal papillary area. On histopathological examination, there were psammoma bodies in neoplastic cells and production of somatostatin. There were also stromal amyloid deposits. We report here a valuable case of carcinoid tumor with type 1 neurofibromatosis accompanied with amyloid deposits.

Multiple tumor suppressor genes are increasingly methylated with age in non-neoplastic gastric epithelia.

A number of tumor suppressor and tumor-related genes are silenced by promoter hypermethylation in gastric cancer. Hypermethylation is not restricted to cancer cells, but is also present in non-neoplastic cells during aging. Such age-related methylation in non-neoplastic gastric epithelia is postulated to constitute a field defect that increases the risk for development of gastric cancer. To quantitatively evaluate age-related methylation in non-neoplastic gastric epithelia, we used a fiber-type DNA microarray on which methylated and unmethylated sequence probes were mounted. After bisulfite modification, a part of the promoter CpG island of four tumor suppressor genes, lysyl oxidase (LOX), p16, RUNX3 and tazarotene-induced gene 1 (TIG1), were amplified by PCR using Cy5 end labeled primers. Methylation rates (MRs) were calculated as the ratio of the fluorescence intensity of a methylated sequence probe to the total fluorescence intensity of methylated and unmethylated probes. Non-neoplastic gastric mucosa was obtained from 24 non-cancer-bearing stomachs at autopsy. MRs ranged from 0.0% to 77.2% (mean, 15.8%) for LOX, 0.0% to 45.8% (mean, 10.0%) for p16, 0.0% to 83.8% (mean, 9.0%) for RUNX3, and 0.0% to 46.1% (mean, 6.6%) for TIG1, and significantly correlated with aging (P < 0.01). The regression curves were: y = 0.013x(2) - 0.6184x + 4.0512, R(2) = 0.5728 (P < 0.001) for LOX; y = 0.0107x(2) - 0.6055x + 5.2943, R(2) = 0.7891 (P < 0.00001) for p16; y = 0.0182x(2) - 1.2234x + 11.566, R(2) = 0.5595 (P < 0.001) for RUNX3; and y = 0.0068 x(2) - 0.3586 x + 2.4306, R(2) = 0.4670 (P < 0.01) for TIG1. Thus, our present results are consistent with the notion that age-related methylation is associated with cancer susceptibility in the elderly. Quantitative analysis of DNA methylation using DNA microarrays is a promising method for risk assessment in the development of gastric cancer.

Quantitative assessment of RUNX3 methylation in neoplastic and non-neoplastic gastric epithelia using a DNA microarray.

Silencing of the RUNX3 gene by hypermethylation of its promoter CpG island plays a major role in gastric carcinogenesis. To quantitatively evaluate RUNX3 methylation, a fiber-type DNA microarray was used on which methylated and unmethylated sequence probes were mounted. After bisulfite modification, a part of the RUNX3 promoter CpG island, at which methylation is critical for gene silencing, was amplified by polymerase chain reaction using a Cy5 end-labeled primer. Methylation rates (MR) were calculated as the ratio of the fluorescence intensity of a methylated sequence probe to the total fluorescence intensity of methylated and unmethylated probes. Five gastric cancer cell lines were analyzed, as well as 26 primary gastric cancers and their corresponding non-neoplastic gastric epithelia. MR in four of the cancer cell lines that lost RUNX3 mRNA ranged from 99.0% to 99.7% (mean, 99.4%), whereas MR in the remaining cell line that expressed RUNX3 mRNA was 0.6%. In primary gastric cancers and their corresponding non-neoplastic gastric epithelia, MR ranged from 0.2% to 76.5% (mean, 22.7%) and from 0.7% to 25.1% (mean, 5.5%). Ten (38.5%) of the 26 gastric cancers and none of their corresponding non-neoplastic gastric epithelia had MR >30%. Most of the samples with MR >10% tested methylation-positive by conventional methylation-specific polymerase chain reaction (MSP). This microarray-based methylation assay is a promising method for the quantitative assessment of gene methylation.